1. Field of the Invention
The present invention relates to a method for analyzing structure safety that can be applied to the multi-hazard safety monitoring and long-term behavior evaluation of an infrastructure such as a bridge, a mass rapid transit, a rail, a water conservation facility, and a side slope. In particular, a measured vibration signal is used to simulate a disaster situation by calibrating the mutual feedback of a structural model, and obtain the critical force exertion and the deformation scale of the structure to evaluate the safety of the structure.
2. Brief Description of the Related Art
Most of the rivers in Taiwan are steep and come with rapid currents, plus the impact of floods caused by heavy rains and typhoons each year, and disaster damages to infrastructures such as bridges, mass rapid transits, rails, water reservation facilities, and side slopes occur frequently.
At present, the studies and technologies for evaluating the safety of a structure adopt a single device, method or process as the base. For example, a “non-destructive structure safety inspection method” as disclosed in R.O.C. Pat. No. 381177 adopts load devices installed at a multiple of points on a bridge deck, and use vibrations produced by striking to reflect different frequency response positions to locate a damaged position of a bridge. An “apparatus for diagnosing and evaluating seismic safety of a building” as disclosed in R.O.C. Pat. No. M302594 uses a decision flow and apparatus to analyze the level of a crack, corrosion, termite rot, or water seepage of a building. A “Construction structure safety testing method” as disclosed in R.O. C. Pat. Publication No. 200741201 comprises one or more wireless intelligent sensors installed on a testing structure for detecting a vibration frequency of the structure, and the vibration frequency is computed and transmitted to another wireless intelligent sensor and then to a remote host computer for its processing, so as to produce data and check the data to determine whether or not the structure is weakened. An “instant safety monitoring system for rail transportation” as disclosed in R.O. C. Pat. Publication No.200848299 comprises a plurality of sensors installed at selected monitoring points of a rail for measuring a vibration signal produced by a vehicle passing through the selected monitoring points wherein the vibration sensors are installed on the rail, and determining an abnormal condition of the rail according to the obtained monitoring parameter and a migration of the natural frequency of the selected monitoring point. As disclosed in U.S. Pat. No. 6,192,758, a “structure safety inspection method” is provided for inspecting damages of a bridge structure, wherein a testing body is placed on a bridge first, and then a motor vehicle is driven and passed over the bridge, and the level of influence of vibrations produced by the traveling motor vehicle to the testing body is detected If the detected influence is lower than a predetermined value, then the bridge is safe; and if the detected influence is higher than the predetermined value, then a dangerous bridge message will be produced. As disclosed in U.S. Pat. No. 5,255,565, a “method and apparatus for monitoring multiple points on a vibrating structure” converts a vibration signal of a bridge into a frequency-domain signal by FFT and calculates the frequency-domain signal to determine whether or not the bridge structure is damaged. As disclosed in Japan Pat. Publication No. 06094583, a “method for inspecting fixed condition or bridge pier and its device” comprising a plurality of sensors installed in both horizontal and vertical directions of a bridge pier, and a FFT is used for detecting the center of oscillation when the bridge pier vibrates, so as to determine whether or not the bridge pier is damaged.
Most of the aforementioned prior arts disclose a way of detecting vibrations of a structure by using a plurality of sensors, and after a fast Fourier transform (FFT) or another equivalent method is used for converting a vibration signal into a frequency-domain signal, the frequency-domain signal is used for evaluating the safety of the structure.
The aforementioned inventions have the following blind spots:                1. The measuring object is limited to a single component of a structure only, but the safety of a whole structure with deteriorated surfaces cannot be determined.        2. The major issue of the practical application of the aforementioned prior art is that the accuracy of measurements at site cannot be integrated with the structure, since the behaviors of the structure are unknown.        3. The structural analysis is carried out by converting the measurement results obtained by the prior art from a vibration signal into a frequency domain by a FFT or any other equivalent method, without mentioning how to overcome the signal distortion problem.        4. In the aforementioned prior arts, the evaluation of a measuring object is limited to a single evaluation method only, and the long-term trend of the structure cannot be controlled. In the meantime, if the structure has encountered disasters for several times, the actual critical condition of the structure cannot be reflected effectively for capturing and analyzing a full time-domain signal.        
In view of the drawbacks of the prior art, the inventor of the present invention based on years of experience in the related industry to conduct extensive research and experiments, and finally designed a method for analyzing structure safety to overcome the aforementioned drawbacks.